feat: Initial project scaffold

Flask API backend for ESP32 sensor fleet:
- App factory pattern with blueprints
- SQLAlchemy 2.x models (Sensor, Device, Sighting, Alert, Event, Probe)
- UDP collector for sensor data streams
- REST API endpoints for sensors, devices, alerts, events, probes, stats
- pytest setup with fixtures
- Containerfile for podman deployment
- Makefile for common tasks

tests/test_api/__init__.py

@@ -0,0 +1 @@
+"""API tests."""

tests/test_api/test_sensors.py

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+"""Sensor API tests."""
+
+
+def test_list_sensors_empty(client):
+    """Test listing sensors when empty."""
+    response = client.get('/api/v1/sensors')
+    assert response.status_code == 200
+    assert response.json == {'sensors': []}
+
+
+def test_get_sensor_not_found(client):
+    """Test getting non-existent sensor."""
+    response = client.get('/api/v1/sensors/nonexistent')
+    assert response.status_code == 404
+
+
+def test_health_check(client):
+    """Test health endpoint."""
+    response = client.get('/health')
+    assert response.status_code == 200
+    assert response.json == {'status': 'ok'}